The present invention relates to a photosensitive material for laser recording (hereinafter referred to as merely xe2x80x9ca photosensitive materialxe2x80x9d) which does not impair the durability of a heat developing part and is improved in traveling property (transportability) during heat development, and also relates to a photothermographic method. More particularly, the present invention relates to a photothermographic photosensitive material which is excellent in development processing stability, accordingly, having good photographic characteristics which can stably reproduce image information, and also relates to a photothermographic method.
There are many photosensitive materials comprising a support having thereon a photosensitive layer, and image is formed by image exposure. Of these materials, techniques of forming images by heat development are widely known as systems capable of realizing environmental protection and simplifying image forming means.
Reduction of waste solutions has been strongly desired in recent years in the medical field from the viewpoint of environmental protection and space saving. Accordingly, photosensitive photothermographic materials for medical diagnosis and photography which can be exposed efficiently with a laser image setter or a laser imager and can form a clear black image exhibiting high resolving power and sharpness have been increasingly demanded. These photosensitive photothermographic materials can offer to customers a simpler and environmentally benign heat development processing system in which the use of solvent system processing chemicals can be done away with.
Method of forming images by heat development are described, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075, and D. Morgan and B. Shely, Thermally Processed Silver Systems, xe2x80x9cImaging Processes and Materialsxe2x80x9d, Neblette Vol. 8, p.2, compiled by Sturge, V. Walworth, and A. Shepp (1969). These photosensitive materials contain a reducible photoinsensitive silver source (e.g., an organic silver salt), a catalytically active amount of a photocatalyst (e.g., a silver halide) and a reducing agent of silver generally having been dispersed in an organic binder matrix. Photosensitive materials are stable at ordinary temperature but when they are heated at a high temperature (e.g., 80xc2x0 C. or more) after exposure, a silver is formed through an oxidation reduction reaction between a reducible silver source (which functions as an oxidizing agent) and a reducing agent. This oxidation reduction reaction is accelerated by the catalysis of a latent image which is generated by exposure. The silver which is formed by the reaction of a reducible silver salt in the exposure area provides a black image, which makes a contrast with a non-exposure area, thus an image is formed.
Heat development is advantageous environmentally in view of not producing waste solutions but has a drawback as to development processing stability (in particular, uneven density). This drawback can be improved by a method using a plate heater but the traveling property during heat development and the liability to damage of a plate heater come to problems in turn.
Accordingly, an object of the present invention is to provide a photothermographic photosensitive material which is excellent in traveling property during heat development and does not damage the surface of a heating means.
Another object of the present invention is to provide a photothermographic method which is superior in transporting property during heat development, does not damage the surface of a heating means and excellent in heat development processing stability.
The above objects of the present invention have been achieved by the following means.
(1) A photothermographic photosensitive material which contains on one side of a support (a) a catalytically active amount of photocatalyst, (b) a reducing agent, (c) a reducible silver salt, and (d) a binder, wherein a matting agent having a softening temperature of from 100 to 500xc2x0 C. is contained at least on one side of the support.
(2) The photothermographic photosensitive material as described in the above item (1), wherein the photosensitive material has a layer containing a catalytically active amount of photocatalyst on one side of the support and contains the matting agent in the surface of the side of the support opposite to the side on which the layer containing a catalytically active amount of photocatalyst is provided.
(3) The photothermographic photosensitive material as described in the above item (1) or (2), wherein the number average particle diameter of the matting agent is from 0.2 to 30 xcexcm.
(4) The photothermographic photosensitive material as described in the above item (1), (2) or (3), which is a photothermographic photosensitive material to be heat developed with a heat developing apparatus, wherein the photosensitive material contains the matting agent in the surface of the side of the support which is touched to the plate heater of the heat developing apparatus, and the dynamic friction coefficient between the plate heater and the surface containing the matting agent at 120xc2x0 C. is 0.30 or less.
(5) The photothermographic photosensitive material as described in any of the above items (1) to (4), wherein the photosensitive material contains gelatin in the surface of the side of the support containing the matting agent.
(6) A photothermographic method which comprises heat developing by making the photothermographic photosensitive material as described in any of the above items (1) to (5) contact with the plate heater.